He is said to have seriously injured a cyclist for inexplicable reasons - now a 35-year-old is in custody.
He wanted to injure a passerby with a knife on the street in Mannheim on Friday, as the public prosecutor and police announced on Monday.
But the potential victim was able to flee.
Then the suspect attacked a cyclist who happened to be passing by and severely injured him with the knife in the lower hip area.
Mannheim - Shortly afterwards, he was temporarily arrested in the immediate vicinity of the crime scene, where he fought violently.
The murder weapon was secured.
According to the police, the 70-year-old cyclist is on the mend after a hospital stay.
The investigating judge issued an arrest warrant on suspicion of attempted manslaughter in the act of dangerous bodily harm and resistance to law enforcement officers.
The motive for the act is still unknown.
dpa